Microstructure and properties of multilayer coatings with covalent bonded hard materials

Single layer thin films of preferably, covalent hard coatings SIG, Si3N4 ha ve been deposited by non-reactive r.f. and reactive d.c. magnetron sputteri ng. By sequential deposition they are combined with metallic hard coatings (TIC, TiN) to multilayer systems with an individual layer thickness of 1-50 0 nm of alternating covalent and metallic hard material layers on cemented carbide or quart substrates. The reactive deposition was carried out at 400 degrees C in an atmosphere of N-2 or CH4 containing Ar by elementary targe ts (Si, Ti). The non-reactive deposited films were grown by the use of stoi chiometric targets (SIC, Si3N4, TiN, TIG) between room temperature and 550 degrees C. The constitution of the single layer and multilayer thin films was studied by XRD, EMPA and HRTEM in dependence on the deposition parameters (substrat e temperature, reactive gas flow) and related to the mechanical properties (hardness, adhesion). SiC films deposited by non-reactive sputtering in a s tochiometric composition at temperatures between 200 and 550 degrees C show an amorphous structure in XRD-studies. The microhardness was measured to 2 600HV0.05 and the critical loads of failure in the scratch test below 30 N for hardmetal/SiC composites. The composition of SiCx thin films deposited by reactive magnetron sputtering has been varied up to x less than or equal to 1.5. The deposition rate of 0.17 nm/s is weakly dependent on the CH4 ga s flow. The films show a hardness up to 3500HV0.05 and critical loads of fa ilure in the scratch test of 70 N. Using XRD studies in Bragg-Brentano geom etry, the (102) line of hexagonal SiC has been found at a substrate tempera ture of 400 degrees C. (C) 1999 Elsevier Science S.A. All rights reserved.